It's at southwestern side of the world map. You'll land on the Mysterious Jungle. After turning an anticlockwise way, you'll find a small house beside a river. You enter this house, and that's an inn. There's a counter at the entrance, but the person serving you is hidden inside. You pay him, and sleep there.
[If you don't beat all the 7 Jinjus, you cannot enter into this inn. Instead, you'll find a man talking about Pedan. Fairy will suggest you to beat the Jinjus before entering Pedan]
You go out after waking up, and that's Pedan! It's a rather big city, with some good weapons and armors (very expensive, too). A scholar lives at the west of the city. You ask him about the location of the Jinju of Darkness.
"I know that," says the scholar. The answer depands on who you are:
Duran & Angela - Dragon Cave, inside the Glass Desert at NW of Artena.
Kevin & Charlotte - Mirage Palace, just inside the Myterious Jungle.
Hawkeye & Riesz - Dark Castle, at the end of the Dark Cave which is south
to Rolant.
There's something special if you're Duran. Inside the armor shop you'll meet Prince Richard (now the King of Forsena) and Roki, your father! "Father!" you say.
"Don't fool me, boy!" says Roki. "My son is just a baby now in Forsena." then Roki turns to Prince Richard.
"Now we know that the King of the Dragon Tribe lives inside the Dragon Cave. Let's go there and stop him from destroying the world." Roki and Prince Richard then goes away.
After that, you may go to one the the above three places. However, there's one thing more important: the second class change. The "special items" to achieve the final class appear now. Open as much treasure boxes as possible after each battle. You may obtain "??? seed". Plant it inside the inn, and you'll give the special item. Since it's a matter of chance, so be patient to wait for your needed item. Go to the central Mana Status inside the Mana Sanctuary to obtain the final class.
Now it's time to go to the above three places. Since I don't know about the Mirage Palace (I'm now playing Charlotte), I'll just talk about the other two places:
Glass Desert & Dragon Cave
Since the enemies inside mostly reaches level 40, so it's a good place to gather experience. Be careful with your HP, especially when you face Nightblade (toughest ninja with Funshinsan which cost you HP400 each). Cast more Light magic, as they'll weak on that. Then you'll see a Mana Stone.
"This Mana Stone isn't broken." says Fairy. Soon it is broken, and the Jinju of Darkness appears. It's a two-face monster (Batman Forever?). Do cast more Light magic. After some time, a third face appears. Deal with the last face, as it will revive the other two faces. After beating it, you can advance to the Dragon Cave.
Soon after entering the Cave, you're stopped by a armored man (you met him when you get the Spirit of Water). Actually it's Duran's father! He's controlled by the dark side (Duran becomes Luc Skywalker?). "Come on, son. Join the dark side!" Roki says. You must beat him to go further. His attack and defence power is very great. His mightiest attack: Lava Sword, costs you HP500+ each. Unless you can cast Light magic on your weapons, it's quite hard to deal with him.
Anyway, you beat him. Then he'll tell his story after he disappears from the Cave. "I'm caught by the Dragon King. Soon I'm controlled by the dark side, follwing him to control the Mana Power. I'm very proud of you, my son. You've overcome the temption of the dark force. Go, Duran, help me to fulfil my wish! Beat the Dragon King!" then Roki dies.
Now you can advance towards the Dragon Cave. Since you cannot refresh yourself inside the Cave, so do get out if your equipment is used up (you can call Flamie at any outdoor places). The structure inside the Cave is rather complex. You must beat some sub-bosses before going further at another point of the cave (I've used over an hour to finish this part). Since you've met those sub-bosses, you should know how to deal with them.
Anyway, if you reach a dark room, that's it. Beat all the monsters inside the room (sometimes there're 20), and the door at the other side opens. The Magician of Red Lotus and Dragon King is at the other end.
"I'll go the Mana Sanctuary to obtain the control of the Mana Power." says the Dragon King, then he disappears. Now you must deal with the Magician. It's the time of revenge for Duran. I'm rather puzzled at this point, because dealing with the Magician is much easier than Roki. Use only physical attack (really good for Kevin), as you cannot hurt the Magician by using magical attack.
After beating the Magician, the Empress of Reason (and Angela if you don't include her) appears. You follow her towards Artena. She feels sorry about what she and the Magician has done. She agree not to attack Forsena anymore.
Dark Cave & Dark Castle
Again, the monsters inside are rather tough. Since there isn't any outdoor places, it's rather difficult to get out of the cave. Fortunately, there're two golden Mana Statues inside (you can refresh yourself). The Jinju is the same as that above. Before entering the Dark Castle, you'll face the Earl! He's, of course, very tough. After defeating him, you'll enter the Dark Castle.
The structure inside the Dark Castle is less complex than that in Dragon Cave. Mostly there's only one way for you to go. Since there isn't any Mana Statue inside, so be careful. Near the top of the Castle, you'll meet Isabella. She turns into a cat-like creature (the Beautiful Beast). She's even tougher than the Earl. My brother used half an hour to deal with her.
After dealing with the tough Beast, go upstairs until you reach the roof of the castle. The Prince of Darkness appears.
"I'll wait for you at the Mana Sanctuary." he says. "See if you can save this world!" then he disappears, and you'll go back to the entrance of the Dark Cave. Leave here using Flamie.
That's all this time, folks